HTML Tag Checker by ACHN is a free Chrome add-on designed to validate HTML start and end tag pairs. This tool is particularly useful for users dealing with segmented HTML or forms submitted via POST, as it operates without external communication. When a tag pair is incorrect, the tool allows users to jump directly to the relevant positions of the start and end tags, facilitating easy correction.

Key features include a communication log that displays detailed content information, automatic HTML tag checking for HTML content, and error color coding. Yellow indicates a warning for tags that should ideally be fixed, while red denotes errors that must be corrected. The tool also offers customizable settings for tag detection, font checks for text content, and the ability to filter logs by URL or content type, ensuring a user-friendly experience.